man bitmap_mask_color () - Returns the mask color of the specified bitmap. Allegro game programming library.
NAME
bitmap_mask_color - Returns the mask color of the specified bitmap. Allegro game programming library.
SYNOPSIS
#include <allegro.h>
int bitmap_mask_color(BITMAP *bmp);
DESCRIPTION
Returns the mask color for the specified bitmap (the value which is skipped when drawing sprites). For 256-color bitmaps this is zero, and for truecolor bitmaps it is bright pink (maximum red and blue, zero green). A frequent use of this function is to clear a bitmap with the mask color so you can later use this bitmap with masked_blit() or draw_sprite() after drawing other stuff on it. Example:
/* Replace mask color with another color. */
for (y = 0; y h; y++)
for (x = 0; x w; x++)
if (getpixel(bmp, x, y) == bitmap_mask_color(bmp))
putpixel(bmp, x, y, another_color);